A simple way to reduce the fleet in a hurry would be to require that much of the non-essential fleet of ordinary cars and twucks be NON-AIRCONDITIONED. This would dramatically reduce the demand for a gubmint vehicle by those who probably don't do anything more than drive it to and from work each day, and it would CERTAINLY reduce the impulse for "workers" to use such cars for pleasure driving on the weekend.
As a f'rinstance, most of the telephone company vehicles around here have no a/c. And you sure don't see too many of them at the kids' soccer meets on Saturday mornings.
Michael
Or, just paint all of em pink......that'll stop personal usage.